hw/misc/stm32l4x5_rcc: Initialize PLLs and clock multiplexers

hw/misc/stm32l4x5_rcc: Initialize PLLs and clock multiplexers

Instantiate the whole clock tree and using the Clock multiplexers and
the PLLs defined in the previous commits. This allows to statically
define the clock tree and easily follow the clock signal from one end to
another.

Also handle three-phase reset now that we have defined a known base
state for every object.
(Reset handling based on hw/misc/zynq_sclr.c)

Signed-off-by: Arnaud Minier <arnaud.minier@telecom-paris.fr>
Signed-off-by: Inès Varhol <ines.varhol@telecom-paris.fr>
Message-id: 20240303140643.81957-5-arnaud.minier@telecom-paris.fr
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>